Dinghy Design: Open 60 influence?

[Doug Lord]

It seems this concept is coming full circle - hopefully recognizing that two daggerboards have much more drag than one, and a central lifting T-foil is the optimal configuration for providing symmetrical lift and low drag performance on both tacks. Continuing the last few degrees in this circle the exercise arrives back to the Moth configuration.

--
CutOnce

=============================
The curved lifting foil concept ,whether the single foil system just discovered or the T2 dual foil system discussed earlier are primarily, at this stage, foils that allow vertical lift and lateral resistance. The vertical lift is NOT a full flying system like the Moth-it is "foil assist" where a single foil can be designed to lift about 80 % of the boats total weight including crew.
In either case only a single foil is used at one time-much simpler and stronger than a t-foil. The curved foil allows adjustment of the lift profile of the foil in a way that is impossible with a t-foil/daggerboard system. The area of the foil needed for vertical lift can be eliminated 100% while still leaving the foil area required for lateral resistance. Not only that but the nature of the system is that the vertical lifting area can be reduced/changed incrementally. In both the Single foil system and the T2 dual foil(one used at a time) system, the foils retract 100%-not possible with a Moth type system.
--
It may be possible, as more research is done on these systems, to design a full flying version but the system at present seems ideal for "foil assist" where
the foil reduces wetted surface-reducing drag significantly.
--
The T2 dual board system(one board used at a time) has another major design benefit and that is that it increases righting moment thereby increasing the boats' power to carry sail. That's a more substantial power increase than any other system available for monohull use.

Rough sketches below, left to right- T2 dual foil system on unique hull(one foil used at a time), Single foil system-foil is an asymmetric section and slides across the boat in a partially open continuous athwartship curved trunk.

click on image:

 

[CutOnce]

================
Well, that didn't take long: with the board partially retracted, on a two person boat, two people could stand near where the board comes out of the hull braced against the board and hull and use a righting line(s) like a multihull and pull the boat back up.
Sorry, but that is not accurate.
This would actually work better than a "normal" daggerboard or one with a t-foil on it since no one would have to climb up out of the water onto a slippery board-the curved board would be just a few inches submerged-not sticking out of the hull at arms length above the water. And using the junction of the hull and board would help to keep the crew in place as they lean back with the righting line(s).

Rough sketch showing righting system( click on image) :

You have a 50/50 chance of the curved board being on the "top" side of the capsize. What happens then? Do you plan on the boat only sailing on port tack? Do you plan on turtling all capsizes on the wrong side? Will this require a minimum 25'-30' water depth to allow for mandatory turtling to get the board on the "down" side?

Like all these nonsensical "Internet" virtual sailing scenarios, just build the thing and prove it works on the water. Proof is in the pudding, not the writing.

--
CutOnce

 

[Doug Lord]

You have a 50/50 chance of the curved board being on the "top" side of the capsize. What happens then? Do you plan on the boat only sailing on port tack? Do you plan on turtling all capsizes on the wrong side? Will this require a minimum 25'-30' water depth to allow for mandatory turtling to get the board on the "down" side?

Like all these nonsensical "Internet" virtual sailing scenarios, just build the thing and prove it works on the water. Proof is in the pudding, not the writing.

--
CutOnce

-----------------------------
Thanks for the comments. The single curved board slides easily athwartship in the partially open, continuous, curved trunk and could be moved by the crew if there was a need. The boat would not turtle because the rig design prevents that.
The single board system was just discovered(invented) yesterday. It was posted because this is a design forum and the single curved foil system represents a new type of design for a vertical lift producing foil that also develops lateral resistance for specific application to a monohull dinghy. As best I can tell, there is nothing like it anywhere and it appears, from a design perspective, to be a dramatic improvement on a "normal" daggerboard.
--
Since I already have a number of patents I'm convinced that should I have chosen to do so I could patent this system. I think the patent system has gone to hell and I have no desire to pursue that opportunity. I'd rather share the design(includes the T2 as well) publically and begin a design dialogue here on boatdesign on the off chance that others may benefit from the system and any experimentation that is done with it.

 

[tabman]

I see Chris's point.

Would you have to swim around the boat to move the board and then swim back around to climb on it to right it?

From my dinghy racing days I remember the boat blowing over again when trying to recover from a capsize to windward in really windy conditions. It could get pretty tiring.

I was a fit and hefty boy back in the day and most times just hauling myself out of the water at the tip of the dagger or centerboard was enough to right a Laser, 420, Sunfish etc without having to actually climb on top of it. Given the length, leverage and height above the water of a conventional board a righting line was never needed for almost all weights of sailors.

The ability to quickly and safely recover from a capsize is a key point in the success of any recreational or racing small sailboat.

Tom

 

[Doug Lord]

I see Chris's point.

The ability to quickly and safely recover from a capsize is a key point in the success of any recreational or racing small sailboat.

Tom

---------------------
Who is Chris? "Cut Once" used to be "Bistros" aka "Bill S".......
---
The point that the boat needs to be rightable is a good one and fairly obvious even though I had not considered it yesterday from the time I came up with the system and when "Once" brought it to my attention.
I'm quite satisfied with the initial righting system I subsequently came up with-moving the board is very simple as is using the righting line.
However, it may be possible to right the boat by just hanging from the extended board.
If the board was retracted or on the wrong side when you capsized you would have to move it, of course-very easy to accomplish. Same thing on a centerboarder with the board retracted when it capsizes.

 

[tabman]

I must have had Cut Once mixed up with someone else (senior moment).

 

[Doug Lord]

A summary of thoughts on a single curved foil used on a dinghy for lateral resistance and vertical lift-so far-version 2:

1) First application I've found where a single curved foil could replace the two foils required in every other current application of curved daggerboards,
-
2) Lots of potential, during the design process,to play with the radius of the curved board to maximize or minimize vertical lift,
-
3) Seems that it may be superior to a "normal" daggerboard in every case including storage(retraction w/o hitting the boom etc),
-
4) Problems include how to grip the board to slide it from one side to the other.
Might be possible to use some sort of hand crank, line that rotates a drum between the two sides of the continuous trunk or? Needs more thought.
-
5) Despite my first impressions earlier it does not appear to be able to increase righting moment significantly(as does T2 dual board system), though this may change as the idea is refined. At the same time, the single curved foil does NOT decrease righting moment as does a curved lifting foil on a multihull.
-
6) When considering this single curved board system and the T2 dual board system it becomes abundantly clear that the use of curved lifting foils are not only possible on dinghies but can offer significant performance potential. By using innovative design these boards can be incorporated in dinghies from "performance daysailers" to scows to all out high performance twin trapeze dinghies(see previous page).
-
7) a boat using the single foil would be simple to right regardless of whether the boat capsizes to leeward or to windward using a righting line or maybe just crew weight hanging on the foil.
-
8) a major design advantage of the single curved foil(with its continuous, partially open, athwartship curved trunk) compared to a t-foil used for "foil assist" is that in conditions where vertical lift produces too much drag the foil can be partially retracted eliminating the unwanted drag due to vertical lift. In addition, the foil can be retracted a small amount at a time to "tune" the vertical lift to the conditions. To further aid in this it appears that a system can be used that would adjust the angle of incidence of the vertical lifting portion of the foil by designing the athwartship, partially open, continuous trunk for this facility.
-
9) as in the T2 version discussed earlier a retractable gantry supporting a small t-foil rudder would probably be an asset in pitch control for a dinghy using the single curved foil. A unique, rotating, rudder system where the rudder trunk actually rotates 180 degrees may be possible to allow the t-foil to be retracted 100% reducing unnecessary drag in light conditions. The rudder would still slide up and down within the trunk. It looks like a system like this could be done fairly simply and robustly-not much more complication than a kick up rudder design. More on this to come.
-
10) At least two dinghy designs use sliding seats or planks for movable ballast(crew): the IC and the Skate-there are probably others. I think a variation on this-a sliding bench seat- may be the best way to incorporate movable ballast on a performance boat using these foils-at least on a performance daysailer. That's why I included it on the T2. It has occurred to me that the moving of the seat from the edge of the cockpit to full out could provide a method of automatically
extending/retracting T2 foils or moving the single foil from side to side without requiring a dedicated effort by the crew. In other words-when the crew moves the seat they move the foil or foils as well. Seems like this would be a relatively simple thing to implement and would make handling the foil(s) a piece of cake. I'm going to look into this further....

 

[Doug Lord]

9) as in the T2 version discussed earlier a retractable gantry supporting a small t-foil rudder would probably be an asset in pitch control for a dinghy using the single curved foil. A unique, rotating, rudder system where the rudder trunk actually rotates 180 degrees may be possible to allow the t-foil to be retracted 100% reducing unnecessary drag in light conditions. The rudder would still slide up and down within the trunk. It looks like a system like this could be done fairly simply and robustly-not much more complication than a kick up rudder design. More on this to come.
-

------------------------
I've thought more on this and if the gantry is similar to the one being used on the little MPX 12 and SRT(see pix below) it can be modified slightly so that it is just a matter of sliding the gantry out and reinserting it to turn the rudder upside down removing the t-foil from the water in light conditions. The tiller would be "unplugged" and plugged back in as well.
Another version of the system would allow an insert in the circular part of the gantry to be rotated from the cockpit with a different type of tiller design.
At any rate, one or the other of these systems would probably work well for reducing wetted surface on a T-foil rudder that is part of a plug-in gantry as shown below:

 

[Doug Lord]

Dinghy Design: Open 60 influence?-single curved lifting foil

The more I've thought about this the more I like it. A single curved foil used in a dinghy, perhaps in combination with a small rudder T-foil, for "foil assist" seems to have the potential to offer a performance increase for monohull dinghies second only to the bi-foiler arrangement used on the Moth and R Class foilers.
The single curved foil would be made in one piece with an asymmetrical section which would be much less expensive than the main foil used on bi-foilers. The single curved foil may be able to be designed into a performance dinghy in a way that a rudder t-foil is not needed*-which would be the ultimate in a vertical lifting system for reducing wetted surface/drag in terms of cost and simplicity since this kind of foil is completely retractable making beach sailing a piece of cake. It is also fully adjustable in terms of how and when it lifts vertically. There is nothing that I've found in a single foil system that offers so much in so simple a package.
And some day we may all owe a debt of gratitude to Guillaume Verdier and his curved lifting foils on the BWR race leader V3!

* Generally, I've always considered that to take full advantage of the vertical lifting capabilities of a foil like this that the sail area required would tend to create a pitching problem that would be best solved using a rudder t-foil. But I don't think that is correct in every case. The curved lifting daggerboard could be placed significantly further forward than could a "normal" daggerboard-almost right up to the mast. Then by balancing the size of the board and rudder to keep the helm with just a touch of weather helm ,the vertical lift from the foil will act far enough ahead of the boat+crew CG to control pitch without a rudder t-foil. The result would be a significant cost reduction coupled with the performance advance of the curved lifting foil. Where a "normal" daggerboard can get in the way of the vang and or boom because it sticks up so high this foil would not-even when fully retracted in its partially open,curved, continuous side to side trunk.

---
Rough sketch below: this shows the board fully retracted in the curved trunk-click on image:

 

[Munter]

Doug - are you familiar with the term "irrational exuberance"?

What happens during a tack? Presumably you will say that the skipper simply raises and then lowers the board during the act of completing the tack. Your enthusiam suggests you do not consider the complete loss of lateral area to act as a pivot point a concern. Have you tried tacking a boat with the centreboard raised?

Alternately, if you are going to move the board before or after a tack how will it budge when under load? The whole 15 cm of board you seem to show actually sitting inside the hull when the board is in position would be so loaded up (and not, in my view, a structurally sensible arrangement) that it would be impossible to move. It would also be devoid of handles or grips because it needs to be immersed and hydrodynamic on the other tack.

Have you a solution for these issues or have they not been considered? Regardless of the reality of any of your imagined performance increases, I suggest that the obvious handling issues would be enough to make it obvious that this configuration is not "superior to a "normal" daggerboard in every case" as you have suggested it "may" be in your lengthy posts above.

 

[Doug Lord]

Design Design: Open 60 influence!

Have you a solution for these issues or have they not been considered?

--------------
Have you ever sailed a boat with twin boards? I have as crew-the skipper would never allow two boards down at once! One up one down in a split second. Its a matter of technique. On this boat the board will move quickly and easily during a tack- there would be less that a half second where the board is not in its proper upwind position.
I'm working on a system where the board movement is automatic and partially controlled by seat movement and/ or the crew. Tacking with this automatic system,should it work well, will be almost as simple as tacking with a normal board.
Moving the board is a small price to pay for a one piece asymmetric lifting foil whose characteristics are 100% adjustable from full lift to no lift. Small price to pay for a lifting foil system that is 100% retractable. This foil system has the potential of significantly outperforming a comparable boat with a "normal" daggerboard upwind and downwind. The benefits drastically outweigh the relatively insignificant effort to move the board.

 

[Munter]

Yes Doug, as it happens I have sailed boats with twin daggerboards and my preference is to put the windward one down before tacking. Cats are different to monos though. In any case, my preference is to minimise the number of things that must be done in a tack where extra steps just increase the likelihood of a snag.

Is your experience on a scow with pivoting centreboards by chance? Do you see any difference in the operation of a centreboard to the operation of a daggerboard? I know which one I find easier to operate. On scows, North's tuning guide appears to say put both boards down (though not too early to minimise drag). No mention of lifting both boards there. http://www.onedesign.com/tuningguide/pdf/north-escow-tuningguide-low.pdf

The proposed configuration requires that board area be dropped to zero, right when the boat is supposed to be pivoting around it. Pretending this problem doesn't exist by saying that its only a split second doesn't really work for me. In reality it won't be a split second, particularly if you try to link it to your infamous sliding bench seats. Next time you go sailing on a single handed dinghy with 160 sqft of sail with a daggerboard, please try lifting and lowering the board as you complete a tack. I predict you'll need a wetsuit.

Alternately - go ahead and build it and demonstrate it. If you have some much faith in the design surely you can't turn down the opportunity to show the claimed superiority both upwind and down over boats with mere daggerboards.

 

[Gary Baigent]

Daniel Charles drew up a similar arrangement on one of his 55 foot proa designs at least 30 years ago - same concept as yours Doug, except his went fore and aft - which allowed one board to do the job on differing tacks/shunts ... but in reality, it never happened, too many problems and he settled for a more conventional two board arrangement.
Just curious, how are you going to swing that 180 degree board across from shifting seat movements? ... because you can't have hole handgrips cut into the board ends, (drag, turbulence) or knobs sliding in slots (ditto) maybe lines set into the board (drag, bad hydrodynamic shape, turbulence) - I think there are far too many Sod's Law of the Sea problems, Doug.

 

[Doug Lord]

Design Design: Open 60 influence?

Just curious, how are you going to swing that 180 degree board across from shifting seat movements? ... because you can't have hole handgrips cut into the board ends, (drag, turbulence) or knobs sliding in slots (ditto) maybe lines set into the board (drag, bad hydrodynamic shape, turbulence) - I think there are far too many Sod's Law of the Sea problems, Doug.

=====
Haven't worked on it long enough to draw that conclusion, Gary-just came up with the idea a couple of weeks-or so-ago!
I'm not 100% sure yet. I'm fairly certain there is a way, though.


PS- Gary, any pictures, sketches from Daniel Charles?

 

[Doug Lord]

Design Design: Open 60 influence!

1) Yes Doug, as it happens I have sailed boats with twin daggerboards and my preference is to put the windward one down before tacking. Cats are different to monos though. In any case, my preference is to minimise the number of things that must be done in a tack where extra steps just increase the likelihood of a snag.

2) Is your experience on a scow with pivoting centreboards by chance? Do you see any difference in the operation of a centreboard to the operation of a daggerboard? I know which one I find easier to operate. On scows, North's tuning guide appears to say put both boards down (though not too early to minimise drag). No mention of lifting both boards there. http://www.onedesign.com/tuningguide/pdf/north-escow-tuningguide-low.pdf

3) The proposed configuration requires that board area be dropped to zero, right when the boat is supposed to be pivoting around it. Pretending this problem doesn't exist by saying that its only a split second doesn't really work for me. In reality it won't be a split second, particularly if you try to link it to your infamous sliding bench seats. Next time you go sailing on a single handed dinghy with 160 sqft of sail with a daggerboard, please try lifting and lowering the board as you complete a tack. I predict you'll need a wetsuit.

===============
1) The single curved board does require that it is moved from tack to tack. In return for which you get a fully retractable, fully adjustable lifting foil capable of significantly reducing drag/increasing performance.

2) My experience on a scow was with a skipper who would not tolerate two boards down at one time. When done right there was a split second when the boat was passing head to wind where there was no board down. Worked for him.

3) There is no pretending involved. No irrational exuberence either. Just the absolute confidence that this board system will work well in a tack. And it will work much better, with far superior results in terms of speed, compared to a "normal" board upwind and downwind. No matter how you cut it you can't disparage the fact that a board system like this has enormous potential to increase speed while reducing drag. But it does more than that. It allows the board to be retracted without getting in the way of the vang or boom. It is the only lifting foil solution I know of ,for a monohull, that allows the system to be 100% retracted*. It is the only lifting foil solution I know of that allows a one piece asymmetrical board.
The advantages of a single curved lifting foil far outweigh any imaginary(poor tacking performance) or real(having to move the board) disadvantages.

* The DSS system develops vertical lift as well as adding to righting moment and is 100% retractable. However, it is not a stand alone system as is the single curved lifting foil which develops both vertical lift and lateral resistance.

=========================
4/4/11----

Congratulations to V3(Virbac-Paprec 3) and Peyron and Dick as well as the designer Verdier/VPLP on being the first monohull keelboat to use curved lifting foils to win a round the world race! A great milestone in sailboat design showing the value of the application of lifting hydrofoils in monohulls!